Soil Behavior Research Articles

Simulation of the biocide distribution in soil using PELMO coupled with COMLEAM.

Biocides, applied in building materials as antimicrobial protectants, can be leached out by rain, presenting substantial environmental risks as confirmed by studies on aquatic environments. However, these biocides are consistently released throughout the year in a diluted form, posing unique challenges for the prediction of transport, transformation, and ecotoxicity assessment in soil. To address this challenge, we combined COMLEAM, which predicts leaching from facades into the soil, with the FOCUS PELMO pesticide model to predict biocide distribution in soil. The study predicted the concentration of the commonly used biocides 1,2-benzisothiazol-3(2H)-one (BIT), 2-n-octyl-4-isothiazolinone-3-one, and terbutryn at various soil depths over 600days, thereby evaluating the influence of different leaching simulations, absorption, and degradation kinetics on the PELMO simulation results. The findings suggest an effective simulation of biocide behavior in soil, with a tendency to overestimate the risk associated with short-acting in-can preservatives like BIT and provide more precise predictions for long-acting film preservatives. Biocide concentrations showed little variance in the upper layers and increased discrepancies at greater depths. This integrated approach provides a cost-effective means for predicting environmental risks and formulating management strategies, especially when paired with experimentally determined soil-specific degradation and absorption values.

Modeling suction of unsaturated granular soil treated with biochar in plant microbial fuel cell bioelectricity system

There is an initiative driven by the carbon-neutrality nature of biochar in recent times, where various countries across Europe and North America have introduced perks to encourage the production of biochar for construction purposes. This objective aligns with the zero greenhouse emission targets set by COP27 for 2050. This research work seeks to assess the effectiveness of biochar in soils with varying grain size distributions in enhancing the soil–water characteristic curve (SWCC). This work further explores the effect of different combinations of biochar content (0 to 15 mass %) on the bioelectricity generation from biochar-improved plant microbial fuel cells (BPMFC). Additionally, different machine learning models such as the “Gradient Boosting (GB)”, “CN2 Rule Induction (CN2)”, “Naive Bayes (NB)”, “Support vector machine (SVM), “Stochastic Gradient Descent (SGD)”, “K-Nearest Neighbors (KNN)”, “Tree Decision (Tree)”, “Random Forest (RF)”, and “Response Surface Methodology” (RSM), have been developed to predict SWCC based on soil suction, electric current, electrical potential, volumetric water content, temperature, and bulk density. The newly established model demonstrates a reasonable ability to predict SWCC and a cheaper technology in predicting the suction of unsaturated soils in relation to the studied bioelectric factors of the BPMFC. Overall, in this research paper, the GB, SVM and CN2 outclassed the other regression techniques in this order thereby proposing the cheapest technology with the highest performance index to predict the SWCC behavior of unsaturated soils in a BPMFC system.

Behavior of Bentonite-Sand Mixture Soil Subjected to History Load

Behavior of Bentonite-Sand Mixture Soil Subjected to History Load

Seepage and stability analysis of hydraulically anisotropic unsaturated infinite slopes under steady infiltration

An analytical model is derived for predicting the flow field and stability of an unsaturated infinite slope subjected to steady infiltration. The proposed model is novel because it accounts for the hydraulic anisotropy of unsaturated soil. The governing equation for steady-state seepage in an infinite slope is established in terms of matric suction under a constant surface flux boundary condition. On the basis of the available experimental findings on the hydraulic anisotropy behavior of unsaturated soils, the relative hydraulic conductivity for a soil under unsaturated conditions with respect to the soil at saturation is postulated to be a direction-independent scalar. This postulation simplifies the governing equation to a form that is directly solvable via the relative hydraulic conductivity and the saturated hydraulic conductivity tensor. To enable sophisticated applications, an exponential law and a power law that are well established in the unsaturated soil literature are used to relate the relative hydraulic conductivity to the matric suction and the effective degree of saturation, respectively. Closed-form solutions are derived for the matric suction, the flow net (potential function and stream function), and the effective degree of saturation. Analytical solutions are also derived for the soil unit weight and overburden stress. These solutions are incorporated into the unsaturated infinite slope stability formula constructed on a suction stress-based effective stress failure criterion. Hydraulic anisotropy has been shown to directly affect the flow field and the change in matric suction, which, in turn, drastically affects the slope safety factor against shallow landslides. This finding demonstrates that neglecting hydraulic anisotropy can cause a considerable overestimation of the safety factor, resulting in an unsafe slope stability prediction. The proposed model is useful for preliminary evaluation of the long-term stability of unsaturated slopes during wet periods and the antecedent slope conditions for shallow landslide initiation under transient infiltration.

Characterising geomaterial shakedown and related deformation accumulation from cyclic triaxial tests

Permanent deformation accumulation in soils and unbound granular materials under repetitive loading leads to surface rutting in roads and deterioration of track geometry in railways, eventually requiring costly and disruptive maintenance. Cyclic or repeated load triaxial tests are a convenient test method to characterise the permanent deformation behaviour of different soils under high numbers of load repetitions and a large volume of data is available. Existing empirical functions either take no account of shakedown, leading to an over-prediction of deformations at a high number of load cycles, or those that do take account of shakedown contain a high number of regression parameters that make them difficult to use. A simple empirical function with only one input parameter is proposed to characterise the accumulation of permanent axial strain in cyclic triaxial tests on a wide range of geomaterials undergoing shakedown deformations. It is shown to give predictions of a similar accuracy to existing functions at low numbers of load cycles and increased accuracy at high numbers of load cycles. It is shown to be applicable to soils ranging from a high plasticity clay to a rail ballast, across a range of stress states, stress history and strain levels provided that ratcheting deformations do not occur. The single input parameter has a physical meaning and is related to the permanent deformation required to reach the shakedown condition. Since the proposed function predicts the slowing rate of deformation accumulation towards shakedown not covered by the commonly-used existing functions, it could lead to more economical designs of applications involving high numbers of load repetitions. Its broad application to both coarse granular materials and fine-grained soils should streamline the design of applications involving layers of both these material types without the need to change empirical function.

Relationship Between Particle Breakability of Pumice Equivalent to Problem Soil and Deformation Behavior Under Cyclic Shear

Relationship Between Particle Breakability of Pumice Equivalent to Problem Soil and Deformation Behavior Under Cyclic Shear

Strength damage analysis on cement-and-fly ash-treated organic soils subjected to freeze–thaw cycles

ABSTRACT Organic soil is usually required to be improved/treated before engineering construction, especially in cold regions due to deterioration introduced by freeze–thaw cycle. In this study, cement-and-fly ash is adopted as agents to stabilise the organic soil. A photogrammetric method is proposed to accurately reconstruct the surface of these cement-and-fly ash-treated organic soils and measure the volume before and after freeze–thaw cycles (F–T-C). Meantime, unconfined compression (U-C) test was performed to evaluate the performance of these specimens after different numbers of F–T-C, and the influence of organic content on soil behaviour was also investigated. These results indicated that an increase in the cement content enhanced the resistance of the organic soils against volume change before and after F–T-C. A proper adoption of cement-and-fly ash significantly improves the unconfined compression strength (UCS) of organic soils subjected to different numbers of F–T-C. The strength of treated organic soil continuously decreased with increasing content of organic. A model was also established to predict soil stress–strain curves with consideration of the number of F–T-C and volumetric changes after the F–T-C.

Assessment of the influence of nonlinear soil effects on seismic response of RC structures with floating columns considering soil–structure interaction

Nonlinear dynamic properties of soil crucially influence structural responses during seismic events, highlighting the interdependence between soil and structural behavior. Incorporating soil–structure interaction (SSI) significantly increases structural vulnerability, especially in irregular conditions, compared to traditional fixed-base structures. Despite the emerging construction of reinforced concrete structures with floating columns in urban areas, their seismic performance, particularly when considering soil-structure interaction, remains largely unexplored. Therefore, this study aims to investigate the structural seismic response of mid-rise reinforcement concrete structures with and without floating columns situated on multilayered soil deposits, incorporating the effects of SSI. The nonlinearity of the soil materials was modeled using an isotropic hardening elastoplastic hysteretic constitutive model. A three-dimensional numerical investigation, employing finite element nonlinear time history analysis, was conducted to study seismic responses of structures under different configurations and base conditions. The results were presented as the ratio of structural responses with soil-structure interaction to fixed-base responses subjected to earthquake events. Structures with floating columns exhibited 1.43 times higher peak lateral storey displacement and 55% higher inter-storey drift ratio compared to those without, considering soil-structure interaction. The analysis results demonstrated a decrease in base shear values of up to 35% when accounting for SSI effects.

Physicochemical mechanics of disperse porous materials as a new approach to assessing mechanical stability of clay soils

Data are presented on the discrepancy between theoretical calculations and experimental results on assessing the strength of fine dispersed bodies including clay soils. Physicochemical processes operating on the surface of dispersed particles are considered upon interaction of latter with water and the formation of adsorbed water films producing disjoining pressure. The presence of films exerting the disjoining effect controls the development of various types of contacts between soil particles in the course of lithogenesis, i. e., coagulational, transitional, and phase contacts. These contacts are the most important factors influencing the behavior of clay soils. The study dwells on the effect of contact types on the state, deformability and stability of clay soils under external impact. It is concluded that the assessment of clay behavior should be based on physicochemical mechanics, patterns of contact interactions in fine-grained soils, and statistical analysis of experimentally obtained parameters of the mechanical properties of clays.

Compression and water retention behavior of saline soil improved by MICP combined with activated carbon

Saline soil is widely distributed in China and poses significant challenges to engineering construction due to its harmful effects, such as salt heaving, dissolution collapse, and frost heaving. The Microbial-Induced Calcite Precipitation (MICP) method is an emerging environmental-friendly modification that can reduce or eliminate the environmental and engineering hazards of saline soil. To verify the feasibility of the MICP method for improving the properties of saline soil, laboratory tests were conducted to study the effects of salt content, activated carbon content and freeze-thaw cycles on the compression and water retention behavior of MICP modified saline soil. The following conclusions were drawn: calcium carbonate produced from the MICP can cement the soil particles of the modified soil structures, which resists the expansion damage caused by salt frost heaving and reduces soil compressibility. Additionally, calcium carbonate particles can fill pores of the soil structures, which improves the water retention capacity of the modified saline soil. The addition of activated carbon can enhance the MICP reaction leading to further reduction in compressibility and enhancement in water retention capacity of MICP modified saline soil.

Prediction and parametric assessment of soil one-dimensional vertical free swelling potential using ensemble machine learning models

Investigating soil swelling potential is indeed a critical research area in geotechnical engineering, given its significant influence on the stability and longevity of civil structures. This study aims to predict and assess the one-dimensional vertical free swelling potential of soils using ensemble machine learning models. Within the study context, a large dataset encompassing a wide array of soil parameters from 210 soil samples, including moisture content, unit weight, plasticity, and clay content, will be used. These parameters are critical in understanding the swelling behavior of soils under varying environmental and load conditions. The novel approach of this research lies in the application of ensemble machine learning techniques, which offer a robust framework to analyze complex, nonlinear relationships within soil properties. Another key aspect of this research is the parametric assessment, where the influence of individual soil properties on swelling potential is investigated using feature importance and partial dependence analyses. These analyses provide valuable insights into the relative importance of different soil parameters on soil behavior. The outcomes of this study contribute to soil mechanics and machine learning applications in geotechnical engineering and offer practical implications for engineers and practitioners. Besides, the predictive models developed in this study aid in more informed decision-making in the design and construction of civil structures, particularly in swelling-prone areas.

Peat classification by sensitivity to mechanical technogenic impacts

Relevance. The problems associated with the weakening of the bearing capacity of peat soils because of technogenic impacts are very relevant in the development of oil and gas industry facilities in the wetlands of Western Siberia. Separately taken classifications according to undrained strength and sensitivity do not reveal the peculiarities of the behavior of weak soils at the base of structures. Therefore, the authors have proposed a different scheme of their classification. It allows assessing the change in physical and mechanical properties when their natural structure is violated during engineering and geological surveys. Aim. Peat classification in the territories of Tomsk, Novosibirsk and Omsk regions according to indicators of undrained strength and sensitivity to mechanical technogenic impacts. Object. Peat soils of Western Siberia. Methods. In accordance with current standards, the research methods included the laboratory methods for determining ash content, humidity, degree of decomposition, field tests to determine the undrained strength and sensitivity coefficient of soils, the information obtained was analyzed in Excel and Statistica software packages. Results. The authors have carried out the review of russian and foreign classifications in terms of soil sensitivity, as well as methods for determining the characteristics used to calculate it and proposed a classification scheme for changes in strength indicators under mechanical influences on peat soils. The article presents the results of experimental data from field and laboratory studies of the physico-mechanical properties of the most common types of peat, their variability after technogenic impacts is estimated according to the proposed scheme using examples of well-known classifications used in the construction of roads, pipelines and for predicting vehicle cross-country ability in swampy areas. The scope of application of the proposed scheme – engineering geological survey for the design, construction, repair and reconstruction of structures – is recommended.

The Adsorption Process and Mechanism of Benzo[a]pyrene in Agricultural Soil Mediated by Microplastics.

The coexistence of microplastics and benzo[a]pyrene (BaP) in the environment, and their interactions within agricultural soils in particular, have garnered widespread attention. This study focused on the early-stage interactions between microplastics and BaP, aiming to uncover their initial adsorption mechanisms. Despite the significant environmental toxicity of both pollutants, research on their mutual interactions in soil is still limited. This study conducted adsorption thermodynamics and kinetics experiments to explore the effects and mechanisms of various microplastics (polyethylene (PE), polystyrene (PS), and polyvinyl chloride (PVC)) on the adsorption of BaP. Using advanced techniques such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy, this study explored the surface characteristics of microplastics and their interactions with BaP. The results demonstrated that PVC microplastics exhibited the highest adsorption capacity for BaP, which was primarily due to π-π interactions and increased hydrophobicity. In the soil-microplastic blend systems, BaP was predominantly found on microplastics, enhancing the soil's adsorption capacity for BaP, particularly PVC, which showed an adsorption capacity 3.69 times greater than that of soil alone. Density functional theory (DFT) simulation calculations indicated that the binding energy of BaP for PVC pretreated with soil was -59.16 kJ/mol, whereas it was -53.02 kJ/mol for untreated PVC, -39.35 kJ/mol for PE, and -48.84 kJ/mol for PS. These findings suggest that soil pretreatment enhances the adsorption stability of PVC for BaP, further elucidating the potential mechanisms behind the increased adsorption capacity in the soil-microplastic system. These findings confirm that microplastics serve as effective vectors for organic pollutants such as BaP, significantly influencing their environmental behavior in soils, and provide essential theoretical support for assessing the environmental toxicity and migration behaviors of microplastics and associated organic contaminants.

How does lime and rice straw compost application affect arsenic uptake in rice after a century of cropping under flooded conditions?

ABSTRACT Arsenic (As) uptake by rice is mainly controlled by the redox potential, amount of iron- and aluminum-bearing minerals and silicon (Si) availability in paddy soil. These soil properties are altered upon long-term continuous rice cultivation, and differences in soil properties arising from different agricultural management practices can influence As behavior in soils. This study aimed to clarify how long-term soil management with and without liming and rice straw compost application influences As uptake by rice. Soil and rice samples were collected from plots with continuous application of NPK mineral fertilizer with and without lime and from plots applied with NPK mineral fertilizer and lime with 750 and 2250 g m−2 straw compost in a long-term experimental paddy field established in 1926. Concentrations of As in rice shoots and panicles from the 92nd to 97th cropping seasons were determined. Hydrochloric acid (1 mol L−1 HCl)-extractable As and pseudototal As concentrations were also determined in select archived soil samples collected from the 52nd to 97th cropping seasons and for the 97th cropping season, respectively. Arsenic uptake by rice was lowest in the plots with lime and 2250 g m−2 rice straw compost application because application of excess organic amendments induced strong reducing conditions, which resulted in a loss of As and Fe minerals from the soil. In this plot, As uptake was lower in the year when no precipitation occurred over a longer period of days during the mid-summer drainage. Despite the increase in the uptake of Si with the application of rice straw compost, the ability of Si to mitigate As uptake was not apparent. The uptake of As by rice in the plot without liming was lower although this plot had a higher concentration of HCl-extractable As in the soil, possibly because As dissolution under flooded conditions was suppressed by the presence of low-crystalline Al minerals. In conclusion, As uptake in rice decreased with the long-term application of excess rice straw compost and in the absence of liming.

Mechanical Behavior of Marine Soft Soil with Different Water Contents Under Cyclic Loading

This study integrates macroscopic dynamic triaxial tests with microscopic discrete element simulations to comprehensively examine the dynamic deformation characteristics of marine soft soils under cyclic loading. Unlike previous research that typically focuses solely on experimental or numerical methods, this approach combines both techniques to enable a holistic analysis of soil behavior. The dynamic triaxial tests assessed macroscopic responses, including strain evolution and energy dissipation, under varying dynamic stress ratios, confining pressures, and water contents. Concurrently, discrete element simulations uncovered the microscopic mechanisms driving these behaviors, such as particle rearrangement, porosity variations, and shear zone development. The results show that (1) The strain range of marine soft soils increases significantly with higher dynamic stress ratios, confining pressures, and water contents; (2) Cumulative dynamic strain and particle displacement intensify at water contents of 50% and 55%. However, at a water content of 60%, the samples exhibit significant damage characterized by the formation of shear bands throughout the entire specimen; (3) As water content increases, energy dissipation in marine soft soils accelerates under lower confining pressures but increases more gradually under higher confining pressures. This behavior is attributed to enhanced particle packing and reduced pore space at elevated confining pressures. This integrated methodology not only enhances analytical capabilities but also provides valuable engineering insights into the dynamic response of marine soft soils. The findings offer essential guidance for the design and stabilization of marine soft soil infrastructure in coastal urban areas.

Numerical Simulation of Unsaturated Expansive Soil Behavior in a Changing Climate Using a Single Stress State Framework

Numerical Simulation of Unsaturated Expansive Soil Behavior in a Changing Climate Using a Single Stress State Framework

Re-examination and analysis of test data on consolidation of soft soils exhibiting creep with different thicknesses

Accurate prediction regarding the long-term settlements of soft soils is challenging. One of the reasons for this is time-dependent soil behaviours. How to extrapolate such behaviours from thin laboratory testing with limited timescales to an in situ thick soil layer with large timescales is still an ongoing debate, which can be dated back to the work of Ladd and co-workers in 1977. Many experimental results that were previously used to advocate hypothesis A have been re-analysed and found to align with hypothesis B. However, discrepancies remain in some historical data, particularly in the case of Osaka clay retrieved from the seabed under the Kansai international airport islands. This study begins by introducing the main implications and selected existing models for the time-dependent behaviours of soft soil. It then focuses on the re-examination of selected test results from the work of Watabe and co-workers in 2008, supplemented by numerical simulation using isotache models. The analysis emphasises the importance of considering equal initial conditions when comparing data from samples with varying thicknesses. Furthermore, the good agreement observed between measured data and the simulation results using hypothesis B methods demonstrates the validity of hypothesis B for predicting the long-term consolidation behaviour of soft soil both in the laboratory and at field scales.

Effect of silt fines on the undrained monotonic behavior of compacted tuff soil

The present study explores the influence of silt content on the undrained monotonic behavior of compacted tuff. All undrained triaxial tests were performed at both relative densities Dr = 50 and 90% and compacted with the optimum water content on tuff soil mixed with silt in the range of 0 to 50%. Experimental results show that adding fines content (FC) up to 20% increases the resistance of dense compacted tuff (Dr = 90%) by about 35% for 100 kPa of confining pressure, and the addition of 10% silt fines results in a maximum increase of 15.71% in the medium dense state specimen (Dr = 50%). The deviator stress reveals a decrease by adding more than 20% of silt. Moreover, the soil cohesion was found to attain maximum values with the optimum silt percentage of FC = 10% for medium-density samples (Dr = 50%) and FC = 20% for dense samples (Dr = 90%), respectively. Finally, the study showed a direct correlation between the cohesion of the soil prepared in a dense state (Dr = 90%) and the soil’s maximum dry density (MDD). In particular, the maximum dry density corresponds to a higher cohesion.

Unveiling Differences in Seismic Response: Comparative Study of Equivalent Linear and Nonlinear Analyses in the Central Coastal Region of Bengkulu, Indonesia

Seismic response analysis is a key aspect in earthquake geotechnical engineering, as it provides important insights into the behavior of soils when exposedtoseismic forces. This research compares equivalent linear and non-linear models in the central coastal region of Bengkulu, which is known for its complex geology and high seismicity. By evaluating the accuracy and reliability of each model in predicting ground motion amplification,this research aims to provide useful recommendations for seismic design. The research method uses one-dimensional equivalent linear and nonlinear propagation modeling, namely Pressure Dependent Hyperbolic (PDH). The analysis resulted in the parameters of Peak Ground Acceleration (PGA), time history acceleration, spectral response acceleration, and amplification factor. The equivalent linear method consistently produced higher values for peak ground acceleration (PGA), spectral response acceleration, time history acceleration, and amplification factor compared to the nonlinear method. The analysis results show that the equivalent linear PGA values are in the range of 0.32g to 0.63g, while the nonlinear values range from 0.20g to 0.52g. The resulting spectral responses are averaged over the design spectrum within 0.2 s to 0.9 s, which can affect low- to high-ceilinged buildings. The equivalent linear amplification factor has a range of 1.59 to 1.91, while the nonlinear has a range of 0.80 to 1.59. Both methods have their advantages, with the nonlinear approach offering greater accuracy for large seismic events, while the equivalent linear model remains useful for preliminary analysis. Hopefully, these findings will improve the understanding of ground response in coastal areas and provide valuable data for improving infrastructure resilience in earthquake-prone areas around the world.

Effect of Sand Addition on Laterite Soil Stabilization.

Lateritic soils, particularly abundant in tropical regions, have been successfully used in the construction of unbound layers of flexible pavements in Brazil since the 1970s. Despite their potential, these soils are often discarded or only recommended after stabilization processes, based on traditional parameters such as gradation requirements and Atterberg limits. This study investigates the mechanical characteristics of a lateritic soil from Roraima, focusing on its resilient modulus and permanent deformation properties, assessed through repeated load triaxial tests. Specifically, this research examines the effect of adding 20% sand on the mechanical behavior of the material. The results indicate that sand addition did not significantly improve the mechanical performance. The laterite-sand mixture exhibited an average resilient modulus (RM) of 744 MPa, lower than the 790 MPa of pure lateritic soil, suggesting that pure laterite remains suitable for pavement applications. Furthermore, the permanent deformation analysis revealed that the mixture with sand experienced nearly twice the plastic strain compared to pure laterite, which demonstrated superior accommodation under repeated loading. In the shakedown analysis, pure laterite exhibited a more stable performance, indicating greater durability in pavement applications. These findings highlight the importance of understanding the mechanical behavior of lateritic soils beyond conventional testing methods, emphasizing the potential of pure laterite as a viable alternative to enhance the strength and durability of pavement structures.